1. Field of the Invention
The present invention relates to a position detecting system and a position detecting method, and, more particularly to a position detecting system and a position detecting method for detecting, using a magnetic field, the position of a body-insertable apparatus of a capsule type inserted into a subject.
2. Description of the Related Art
In recent years, body-insertable apparatuses such as a capsule endoscope are developed that are inserted into subjects such as a person and an animal and acquire various kinds of information such as images in the subjects and apply some treatment to the inside of the subjects (see, for example, Patent Documents 1 to 4 described below). For example, a body-insertable apparatus including an imaging device is inserted into a subject through the mouth, captures images of the inside of the subject, and transmits obtained images (hereinafter, “intra-subject images”) to an external apparatus arranged on the outside of the subject by radio. An operator can diagnose a symptom and the like of the subject by visually checking the intra-subject images received by the external apparatus.
In a system including the body-insertable apparatus explained above, it is desired to accurately learn the position, the direction, and the like of the body-insertable apparatus for the purpose of, for example, imaging in the subject, identification of a treatment place, and position guidance for the body-insertable apparatus. Therefore, Japanese Laid-open Patent Publication No. 2007-175317 discloses a position detecting system in which a resonance circuit including a coil (L) and a capacitor (C) (hereinafter, “LC resonance circuit”) is provided in a body-insertable apparatus and that detects, with a sense coil provided in an external apparatus, a resonant magnetic field generated by an alternating magnetic field given to the LC resonance circuit from the outside (hereinafter, “driving magnetic field”) to detect the position and the direction of the body-insertable apparatus.